#lang racket/base
(require sugar/unstable/dict xenomorph)
(provide prep)

#|
approximates
https://github.com/mbutterick/fontkit/blob/master/src/tables/prep.js
|#

(define prep (x:struct 'controlValueProgram (x:array #:type uint8)))

(module+ test
 (require rackunit racket/dict racket/serialize "../helper.rkt")
 (define ip (open-input-file charter-path))
 (define dir (deserialize (read (open-input-file charter-directory-path))))
 (define offset (hash-ref (hash-ref (hash-ref dir 'tables) 'prep) 'offset))
 (define len (hash-ref (hash-ref (hash-ref dir 'tables) 'prep) 'length))
 (check-equal? offset 4512)
 (check-equal? len 78)
 (file-position ip 0)
 (define table-bytes #"\270\0\0+\0\272\0\1\0\1\0\2+\1\272\0\2\0\1\0\2+\1\277\0\2\0C\0007\0+\0\37\0\23\0\0\0\b+\0\277\0\1\0\200\0i\0R\0;\0#\0\0\0\b+\0\272\0\3\0\5\0\a+\270\0\0 E}i\30D")
 (check-equal? table-bytes (peek-bytes len offset ip))
 (define ds (open-input-bytes (peek-bytes len offset ip)))
 (check-equal? (dict-ref (decode prep ds) 'controlValueProgram) '(184 0 0 43 0 186 0 1 0 1 0 2 43 1 186 0 2 0 1 0 2 43 1 191 0 2 0 67 0 55 0 43 0 31 0 19 0 0 0 8 43 0 191 0 1 0 128 0 105 0 82 0 59 0 35 0 0 0 8 43 0 186 0 3 0 5 0 7 43 184 0 0 32 69 125 105 24 68)))